Inmates staged a relatively calm — and apparently unprovoked — riot at the Pitchess Detention Center in Castaic causing minor injuries to one deputy and one inmate Friday.

An estimated 125 inmates of the medium security jail’s East facility began barricading doors to the dormitory at about 2 p.m., said acting security captain Carlos Marquez.

One deputy suffered minor injuries to the palm of his hand when he tried to open a can of condensed pepper spray.“He was deploying one of the weapons and it detonated in his hand,” Marquez said.

The injured deputy threw the smoking device into the dorm which then exposed the inmates to harsh fumes, he said.

“They began to barricade the doors and cause a disturbance,” Marquez said about early events in the disturbance. “We tried negotiating but that didn’t do any good.”

Guards ordered them to be back in their bunks but the inmates did not respond.

The inmates did not make any demands during the disturbance, Marquez said.

Guards put the smoking can of gas into the dorm after negotiations failed, he said.

Jail staff had difficulty getting into the dorm, Marquez explained.

“They (inmates) would use their bunks, their mattresses and sheets, anything that would be readily available,” he said.

The dormitory is about 50 feet wide, he said.

Once the gas entered the dorm, guards moved all 125 inmates to a nearby holding area.

Cleanup of the smoke-filled dorm was expected to take most of the night, Marquez explained.

Investigators started interviewing some of the inmates in an effort to determine who started the disturbance and why they did.

“Why don’t know at this point why they did it,” Marquez said. “We don’t know why it was started.

“We’re going to try and identify who the instigators were. If any criminal violations occurred this will also be filed in the report.”

Emergency personnel transported inmate who complained of chest pains to a local hospital. Marquez described the effects of the gas as similar to the effects of pepper spray which causes a burning sensation to the skin and eyes.

A fight broke out in a dormitory and several inmates were injured during the altercation, said Los Angeles County Sheriff’s Deputy Ed Herandez. Paramedics treated them on the scene, he said.

Hernandez does not know what triggered the fight.

The last time jail staff responded to a disturbance in the East dorm — one of four facilities at the center — was in 2006.

Inmates inside the dorm are a mix of convicted men serving out their sentences, some accused of crimes including rape, murder and manslaughter, and men charged with a criminal offense awaiting trial, officials said.